Tricompartment offloader knee brace reduces sagittal plane knee moments, quadriceps muscle activity, and pain during chair rise and lower in individuals with knee osteoarthritis.

The Levitation tricompartment offloader (TCO) knee brace provides an assistive knee extension moment with the goal of unloading all three compartments of the knee and reducing pain for individuals with multicompartment knee osteoarthritis (OA). This study aimed to determine the effect of the TCO brace on sagittal plane knee moments, quadriceps muscle activity, and pain in individuals with multicompartment knee OA. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise and lower to determine differences between bracing conditions. TCO brace use significantly decreased the peak net knee external flexion moment in high power mode, providing extension assistance during chair rise [p<0.001; mean difference (MD) (98.75% CI) -0.8 (-1.0, -0.6)%BWxH] and bodyweight support during chair lower [p<0.001; -1.1 (-1.6, -0.7)%BWxH]. Quadriceps activation intensity was significantly reduced with brace use by up to 67% for the vastus medialis [Z = -2.55, p = 0.008] and up to 39% for the vastus lateralis [Z = -2.67, p = 0.004]. Participants reported significantly reduced knee pain with the TCO brace worn in high power mode compared to the no brace condition [p = 0.014; MD (97.5% CI) -18.8 (-32.22, -2.34) mm]. These results support the intended mechanism of joint unloading via extension assistance with the TCO brace. The observed biomechanical changes were accompanied by immediate reductions in user reported pain levels, and support the use of the TCO for conservative management to reduce knee pain in patients with multicompartment knee OA.

Tricompartment offloader knee brace reduces contact forces in adults with multicompartment knee osteoarthritis.

The levitation tricompartment offloader (TCO) brace is designed to unload all three knee compartments by reducing compressive forces caused by muscle contraction. This study aimed to determine the effect of the TCO on knee contact forces and quadriceps muscle activity in individuals with knee osteoarthritis. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise-and-lower task. A three-dimensional inverse dynamics model of the lower leg and foot was used with a sagittal plane knee model to compute knee joint forces. TCO brace use significantly decreased forces in the tibiofemoral [p = 0.001; mean difference, MD (97.5% confidence interval, CI) -0.62 (-0.91, -0.33) body weight (BW)] and patellofemoral [p = 0.001; MD (97.5% CI) -0.88 (-1.36, -0.39) BW] compartments in high-power mode. Significant reductions in quadriceps tendon force [p = 0.002; MD (97.5% CI) -0.53 (-0.83, -0.23) BW] and electromyography intensity of the vastus medialis [p = 0.018, MD (97.5% CI) -30.7 (-59.1, -2.3)] and vastus lateralis [p = 0.012, MD (97.5% CI) -26.2 (-48.5, -3.9)] were also observed. The TCO significantly reduced tibiofemoral and patellofemoral contact forces throughout chair lower, and when knee flexion was greater than 50° during chair rise in high power. These results demonstrate that the TCO reduces contact forces in the tibiofemoral and patellofemoral joint compartments and confirms that the TCO unloads the joint by reducing compressive forces caused by the quadriceps. Clinical significance: The magnitude of knee joint unloading provided by the TCO is similar to that achieved by clinically recommended levels of bodyweight loss and is therefore expected to result in clinical benefits for knee osteoarthritis patients.

Preliminary Evaluation of a New Orthotic for Patellofemoral and Multicompartment Knee Osteoarthritis.

PURPOSE: Traditional knee osteoarthritis (OA) braces are usually indicated for a minority of patients with knee OA, as they are only suitable for those with unicompartmental disease affecting the tibiofemoral joint. A new assistive brace design is intended for use in a wider range of knee OA patients with heterogeneous symptoms characteristic of patellofemoral, tibiofemoral, or multicompartmental knee OA. The purpose of this case series was to explore whether the use of this novel "tricompartment offloader" (TCO) brace was associated with clinically relevant improvements in pain and function. MATERIALS AND METHODS: A retrospective analysis of individuals with knee OA (n = 40) was conducted to assess pain, function, physical activity, and use of medication and other treatments before and after brace use. Validated outcome measures including the Visual Analog Scale (VAS) and Lower Extremity Functional Scale (LEFS) were used to assess pain and physical function (primary outcome measures). Exploratory measures were used to quantify physical activity levels and use of medication and other treatments (secondary outcome measures). RESULTS: Average total pain (VAS) scores decreased by 36.6 mm and physical function (LEFS) scores increased by 16.0 points following the use of the TCO brace. Overall, 70% of the participants indicated increased weekly physical activity and 60% reported a decrease in their use of at least one other treatment. CONCLUSIONS: Results from this case series suggest that the TCO brace shows strong potential to fill a conservative treatment gap for patients with heterogeneous symptoms of knee OA that are characteristic of patellofemoral or multicompartment disease. Further investigation is warranted.

Characterizing healthy knee symmetry using the finite helical axis and muscle power during open and closed chain tasks.

Understanding healthy joint movement and muscle control, and injurious alterations, is important to determine musculoskeletal contributions to post-injury joint instabilities or altered dynamic joint function. The contralateral limb is often used as a point of reference to determine the effects of knee joint injury. However, it is currently difficult to interpret within subject variability between limbs as this is not well established in the healthy population. There is a continuing need to characterize healthy knee joint mechanics and neuromuscular control to determine the degree of symmetry within healthy individuals. The current study quantified limb symmetry in healthy individuals using the finite helical axis with a unique reference position (rFHA) and electromyography (EMG) approaches, for a closed-chain single leg squat (SLS) and an open-chain seated leg swing. Muscle power and FHA translation, orientation and dispersion were similar between limbs. However, the FHA was located significantly more anterior in the dominant limb relative to the contralateral during both tasks. These between-limb differences in FHA location could be attributed to differences in joint geometry and strength between limbs. This finding provides evidence that healthy knees have asymmetries which have implications for selection of control limbs in studies comparing conditions within and between individuals. Differences identified in dynamic joint function between tasks suggest that the SLS is useful for revealing joint asymmetries due to altered muscular control strategies, while the swing task is expected to highlight asymmetries in joint motion due to altered knee structures following injury.

Biomechanical Study of a Tricompartmental Unloader Brace for Patellofemoral or Multicompartment Knee Osteoarthritis.

Objective: Off-loader knee braces have traditionally focused on redistributing loads away from either the medial or lateral tibiofemoral (TF) compartments. In this article, we study the potential of a novel "tricompartment unloader" (TCU) knee brace intended to simultaneously unload both the patellofemoral (PF) and TF joints during knee flexion. Three different models of the TCU brace are evaluated for their potential to unload the knee joint. Methods: A sagittal plane model of the knee was used to compute PF and TF contact forces, patellar and quadriceps tendon forces, and forces in the anterior and posterior cruciate ligaments during a deep knee bend (DKB) test using motion analysis data from eight participants. Forces were computed for the observed (no brace) and simulated braced conditions. A sensitivity and validity analysis was conducted to determine the valid output range for the model, and Statistical Parameter Mapping was used to quantify the effectual region of the different TCU brace models. Results: PF and TF joint force calculations were valid between ~0 and 100 degrees of flexion. All three simulated brace models significantly (p < 0.001) reduced predicted knee joint loads (by 30-50%) across all structures, at knee flexion angles >~30 degrees during DKB. Conclusions: The TCU brace is predicted to reduce PF and TF knee joint contact loads during weight-bearing activity requiring knee flexion angles between 30 and 100 degrees; this effect may be clinically beneficial for pain reduction or rehabilitation from common knee injuries or joint disorders. Future work is needed to assess the range of possible clinical and prophylactic benefits of the TCU brace.

Error reduction in the finite helical axis for knee kinematics.

Traditionally the FHA is calculated stepwise between data points (sFHA), requiring down sampling to achieve a sufficiently large step size to minimize error. This paper proposes an alternate FHA calculation approach (rFHA), using a unique reference position to reduce error associated with small rotation angles. This study demonstrated error reduction using the rFHA approach relative to the sFHA approach. Furthermore, the rFHA in the femur is defined at each time point providing a continuous representation of joint motion. These characteristics enable the rFHA to quantify small differences in knee joint motion, providing an excellent measure to quantify knee joint stability.